I am using Mcafee Sidewinder 8.2.1 . I want to whitelist some domains or host for email delivery. In that rule sendmail will be disabled. The issue which i am facing is that if I am having issues of email delivery from engrofoods.com then when I check the relay agent of engrofoods.com is giving dynamic IPs also the host of relay is dynamic.

So then what you would need to do is create a seperate rule specifically for these mails. It would use an app defense that did not do the enforcement. Unfortunately since the mail seems to come from dynamic/different IP addresses, host objects may be necessary. Before you implement the host object, please take a look at the following KB article: